1. Field of the Invention
The present invention relates to a light-receiving element for receiving light reflected from an optical recording medium, an optical head using the element, and an optical recording/reproducing apparatus using the element.
2. Description of the Related Art
A light-receiving element used in an optical head has an integrated circuit element in which a light-receiving portion is formed and a circuit board in which the integrated circuit element is mounted. The light-receiving element also has a bonding portion including electrode pads formed on the integrated circuit element, electrode terminals formed on the circuit board, and wires for connecting the electrode pads to the electrode terminals. The light-receiving element also has a cover layer disposed so as to cover an upper side of the light-receiving portion and the bonding portion and extend over the integrated circuit element and the circuit board. The cover layer has functions of protecting wire and relaxing stress. Specifically, the cover layer functions as a protective member that prevents corrosion caused by moisture and short circuit failures in the bonding portion caused by motes, dust, and the like in air.
The light-receiving portion is configured so that it can receive light reflected from an optical recording medium. The light-receiving element converts an amount of the light received by the light-receiving portion into an electric signal by photoelectric conversion, and the light-receiving element outputs the electric signal from the bonding portion. On the basis of the electric signal, a reproducing signal including information recorded on the optical recording medium and an error detection signal used in adjustment of a focusing error or a tracking error of the optical head are generated.
Patent Document 1: JP-A-2005-5363
Patent Document 2: JP-A-2006-41456
Patent Document 3: JP-A-2004-214291
Patent Document 4: JP-A-2005-45051
Patent Document 5: JP-A-2003-309271
Patent Document 6: JP-A-2005-26260
However, in the next generation optical head, it is necessary to shorten a light source wavelength in order to increase recording density. For example, the light source wavelength used in compact disk (CD) apparatus is near 780 nm, but the light source wavelength used in digital versatile disk (DVD) apparatus is near 650 nm. Nowadays, the light source wavelength has been shortened to near 400 nm. Generally, when the light source wavelength is shortened, optical parts' characteristics such as chromatic aberration, transmittance, and durability are varied, those characteristic variation remarkably increases near 400 nm as a boundary wavelength. Accordingly, even when some optical parts are usable in the range of the light source wavelength used in CD apparatus and DVD apparatus, the parts may not be used when using a light source having a wavelength near 400 nm. Specifically, when short-wavelength light having high power is radiated on optical parts, adhesives, and the like using resin for a long time, the resin is chemically changed and the chemical change occasionally causes damages such as a transmittance change, deformation, or the like. Additionally, in order to solve the problem mentioned above, it can be considered that a member using glass instead of resin is disposed on a light path of a laser, but there is a problem that needs high processing costs and assembling costs of the parts.
It is an object of the present invention to provide a light-receiving element that can be manufactured at low cost and in a simple manner and is configured to receive light from a short-wavelength laser source (having a wavelength of 402 nm to 413 nm), an optical head using the element, and an optical recording/reproducing apparatus using the element.